Evidence regarding the integrity of the posterior medial lateral suprasylvian visual area in the cat.

Among the areas of lateral suprasylvian visual cortex in cats defined by Palmer et al. (J Comp Neurol [1978] 177:237-256), PMLS (posterior lateral suprasylvian area) has been the most studied. Although PMLS has strong and well-documented connections with area 17, it is unclear whether these connections extend to its upper visual field representation.

A novel system for recording from single neurons in unrestrained animals.

To observe neural activity in animals engaged in natural behavior, it is often desirable to minimize or eliminate restraint of the animal. We have developed a simple system for recording from single units in unrestrained cats. An implant with multiple guide tubes and a tiny microdrive is placed inside the recording chamber.

Accurate visual guidance despite severe neglect.

Unilateral inactivation of the superior colliculus causes profound neglect. In cats, this neglect has been studied previously using tasks that require gaze orientation to, or detection of, a stimulus appearing somewhere in the visual field of an attentive animal. We investigated how neglect affects a completely different kind of task, visually guided foot placement while walking across a cluttered surface.

The use of visual information for planning accurate steps in a cluttered environment.

When an observer walks across irregular terrain, he uses vision to plan his steps. How far in advance of each step does he acquire the critical information? We trained cats to walk accurately down a cluttered alley, and then turned out the light in mid-trial. Cats usually continued to walk without error for one to four steps, indicating that they had acquired the information to guide each step well before foot contact.

Gaze during visually-guided locomotion in cats.

Visual guidance is often critical during locomotion. To understand how the visual system performs this function it is necessary to know what pattern of retinal image motion neurons experience. If a locomoting observer maintains an angle of gaze that is constant relative to his body, retinal image motion will resemble Gibson's (The Perception of the Visual World (1950)) well-known optic flow field.

Responses in extrastriate cortex to optic flow during simulated turns.

An observer locomoting along a straight path sees a pattern of optic flow in which images move approximately radially outward from his heading point. If the observer turns, the optic flow field changes markedly because each object's image now has a component of horizontal motion added to its "optic flow" motion. We tested the responses of 326 cells in the cat's extrastriate area LS (lateral suprasylvian visual area) to movies simulating the optic flow seen during locomotion in a straight line, and during various simulated turns to the left and right.

Lesions of extrastriate cortex and consequences for visual guidance during locomotion.

One of the functions of the putative motion pathway in visual cortex may be visual guidance during locomotion. Using cats, we have investigated the role of the first area in this pathway, the lateral suprasylvian visual area (LS, often considered analogous to the primate area MT). Visual function during locomotion was tested by looking at the accuracy of foot placement as cats walked down a cluttered alley.